Treatment of dyeing wastewater by inner electrolysis-hydrolysis acidification-contact oxidation-oxidation coagulation integrated process

The inner electrolysis-hydrolysis acidification-contact oxidation-oxidation coagulation integrated process was established for treatment of the dyeing wastewater,the effect of influent pH,contacting time,temperature,Fe/C mass ratio of pall ring filler on COD and colourity removal efficiency was investigated.The performance of each unit was analyzed separately.Results showed that the optimal conditions for inner electrolysis were pH 3,reacted for 120 min,15～20 ℃ and Fe/C was 2,under these conditions,the inner electrolysis achieved perfect efficiency for COD,colourity and TP removal,the biodegradability of dyeing wastewater was greatly improved.In the next hydrolysis acidification unit,the COD removal efficiency was 35% while NH3-N slightly increased,pH was decreased by 0.3 and biodegradability of wastewater was further improved.In contact oxidation process,the effluent COD was dropped to 148-180 mg/L,the removal efficiency of COD and NH3-N was 70% and 95% respectively.The last oxidation coagulation process was applied for further treatment of effluent,after coagulation treated by the best combined reagent,the COD concentration was less than 100 mg/L,which could meet the second class discharge standard of Integrated Wastewater Discharge Standard(GB 8798—1996).